Sorry guys...I need a bit more help...
I checked my service manual tonight for the 2005 crf150f but did not find some of the items you mentioned...at least not by those names.
I'll assume your suggestion is to replace the pilot screw, not the main jet, slow jet, or needle jet.
I'm not sure what the slide plate seal is? Is that the gasket above the throttle valve? I'm assuming if additional air is leaking in that obviously messes with the A/F ratio.
I can check the header washer after reinstall (which looks good, but I'll check for leaks), but what/where is the 'hot start'? I'm not familiar with that term.
Sorry for my ignorance. Thanks again for the help.